//
// Created by Castle on 2025/10/28.
//

#include <iostream>
using namespace std;

int main() {
    // 多分支结构
    double a,b,sum;
    if ( b >= 5) {
        if (b < 10) {
            cout << a * b * 0.9;
        }else {
            cout << a * b * 0.8;
        }
    }else {
        cout << a * b;
    }
    return 0;
}